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Author Topic: Scary Stuff, Scary Stuff....  (Read 1060 times)

Offline Mark Mc

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Scary Stuff, Scary Stuff....
« on: September 28, 2018, 11:42:18 PM »
I have a White Lightning 1/2A plane designed for the Norvel .061that I built three or four years ago.  As I posted in the 1/2A White Lightning thread, I got a hankering to re-electrify it.  So I converted it yesterday with the Brodak power package I had on hand.  It's the Brodak EPS-10 Sport package which is the electric package seeming about right to replace a Norvel .061 engine.  It has the 1560KV 2210/25 motor on a 3S battery with their 18A esc and an APC 7x5E prop.  I used an 800 mAh battery instead of the 1300 mAh suggested to save weight.  I also used an RC transmitter and receiver for speed control.  For attaching the prop, I used the prop saver hub that came with the Brodak motor, as I was flying on asphalt and didn't want to use a collet.

So, as I was at the handle and slowly spinning up the motor for take-off, something scary happened.  At a little over half throttle, the prop saver let go and the prop went flying off.  For me it wasn't so dangerous, but seeing the prop fly off a few inches in front of the person holding the plane (well, it SEEMED like a few inches from out at the center where I was standing) scared the crap out of me. 

I had spun up the motor the night before when I was hooking up the motor leads for proper polarity, and it had no problem.  But, being incredibly embarrassed by what had happened, I put the plane away until I could further analyze what happened.  On my way home, I stopped at the hobby shop and bought some thicker o-rings for the prop saver, but I may just switch to a collet for the prop anyway.  And when I got home, I fired up the computer and checked the Brodak website for the info on the EPS-10 system to make sure I hadn't made a mistake on my components.  But other than the smaller battery and using a receiver instead of a timer, I had the right motor/voltage/esc/prop combination recommended by Brodak.

Scary Stuff, scary stuff.  Next time I go out I'll have a couple of 2S batteries charged up and try those first, but the 3S should be right, right?  And one thing's for sure.  When I test fly it next week, I'll launch from a stooge instead of having a helper hold the model for take-off.

Mark

Offline Keith Renecle

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Re: Scary Stuff, Scary Stuff....
« Reply #1 on: September 29, 2018, 11:31:25 PM »
Hi Mark,

I have a whole bunch of 1/2A models and I only use the smaller APC 6 x 5.5 E props. It's a ground clearance thing for me because most of the Babe Bee size models have short undercart legs. I've run bigger props with those rubber o-rings but at much lower rpm. The other thing in your case could be the R/C system because you'll get full rpm whereas with timers you would normally not get such high rpm. If there is even a small balance issue with the prop, the bigger prop will suffer a little more. I use a small motor with a Kv of 1900 ~ 2000 on the 6 x 5.5 props and they fly nicely. The o-rings do need to be changed regularly as they tend to perish.

My Baby Sparky model is still flying and I've never had any issues with the o-ring. As you can see in the close-up pic, the timer is held on with Velcro which also wraps around the esc on the other side. This model is a bit twitchy so if I made another one I would extend the nose.

Keith R
Keith R

Offline Paul Bray

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Re: Scary Stuff, Scary Stuff....
« Reply #2 on: October 15, 2018, 02:13:45 PM »
Hi Mark,

that problem has been encountered by many people flying RC and apart from the points already made by Keith (which are right on the money) the quality of the black 'O' Rings is also a problem. Added to the at teh fact that they are designed to compress and not stretch and you have a disaster looking for a place to happen.

If you want to use a prop saver and I do use them, a lot, look at using the zip tie method or better still by far is to use TeraBand. This is silicone tube and you cut a slice off to replace the black band. The red stuff is fantastic for this size of prop, really strong although I still use 2 rings but it will also 'give' saving the prop if you have a whoopsy. There is extensive information on the RC Groups site and you can even get a free sample of TeraBand in some countries but if you do have to buy it only a foot will make you hundreds of bands.

On the other hand, what does a prop cost if you buy them in packs of 10 from the far east?? In some cases I just bolt a prop on and trow some spares into my case, the broken blades make great paint stirrers or glue spreaders!

Paul


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